Method and system for analyzing gait and providing real-time feedback on gait asymmetry

ABSTRACT

A method and system for analyzing gait asymmetry between left and right feet of individuals by measuring and comparing stance phase time and/or stance phase force between left and right during gait, and providing real-time sensory feedback if stance phase time/force inequality exceeds a predetermined threshold.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.12/407,967, entitled “Method and System for Analyzing Gait and ProvidingReal-Time Feedback on Gait Asymmetry,” filed Mar. 20, 2009, whichapplication claims priority to and the benefit of U.S. ProvisionalPatent Application Ser. No. 61/070,412, filed on Mar. 20, 2008. All ofthe aforementioned applications are incorporated by reference herein intheir entirety.

BACKGROUND

Field of the Invention

The present invention relates generally to gait assist devices.

Related Art

Asymmetry of gait refers to a difference in gait parameters between theleft and right lower limbs, including both asymmetrical distribution ofweight, as well as unequal time spent on the left and right feet duringstance. Asymmetric gait is common in individuals with unilateral lowerlimb amputations, post cerebral accident victims, stroke victims, andlower limb orthopedic surgery patients. Asymmetric gait has been linkedwith chronic overloading in the non-amputated limb. Such overloading canoccur because less time is often spent on the amputated leg and ashorter step length is often taken on the intact leg. Additionally, gaitasymmetry has been shown to increase with walking speed which canaccount for greater loading of the joints in the intact limb ofunilateral amputees.

This asymmetry of gait and subsequent overloading of the non-amputatedlimb has been associated with osteoarthritis in the knee of thenon-amputated limb, which can have a profound impact on an individual'squality of life. Research suggests this higher prevalence ofosteoarthritis may be due to the increased force in the intact leg whichresults from asymmetrical gait. A possible explanation for theasymmetric force is the lack of proprioceptive feedback provided throughthe prosthetic as compared to the normal biological ankle.Unfortunately, interventions to improve gait symmetry in the amputeepopulation have historically been qualitative and have focused ondescriptions of symptoms resulting from asymmetrical gait instead ofpossible preventive therapy or treatment.

SUMMARY OF THE INVENTION

The inventors of the present invention have recognized that it would beadvantageous to develop a method and/or system for analyzing gaitasymmetry (between left and right feet) of individuals, such asunilateral lower limb amputees, post cerebral accident victims, strokevictims, or lower limb orthopedic surgery patients, by measuring andcomparing stance phase time and/or stance phase force between left andright feet during gait, and providing real-time sensory feedback ifstance phase time/force inequality exceeds a predetermined threshold.

The inventors of the present invention have recognized that it would beadvantageous to develop a method and device for evaluating the asymmetryof gait of a user and providing feedback in real time if the asymmetryis over a specified threshold to allow lower extremity amputees toidentify and correct gait asymmetries. Additionally, the inventors ofthe present invention have recognized that it would be advantageous todevelop a method and device to detect the amount of time an individualspends on their left foot compared to their right foot to detectasymmetry of stance time or a limp, and to provide real time feedback ifthe asymmetry is over a specified threshold. Additionally, the inventorsof the present invention have recognized that it would be advantageousto develop a method and device to detect changes in total force betweenthe two feet to detect asymmetry of stance loading, and to provide realtime feedback if the asymmetry is over a specified threshold. Moreover,the inventors of the present invention have recognized that it would beadvantageous to develop a method and device that will measure stancephase times and applied loading through force sensors coupled to anelectronic processor that will determine if a gait asymmetry exists andprovide feedback to the user via the electronic processor. Furthermore,the inventors of the present invention have recognized that it would beadvantageous to develop a method and device to analyze stance phaseforce symmetries, stance phase times, bilateral forces, and degree ofasymmetry.

The invention provides a method for analyzing gait and providing realtime feedback on gait asymmetry. Sensor data is received from aplurality of sensors disposed within left and right shoes when the shoesare moved through gait motions by a user of the shoes. The sensor datais analyzed with an electronic processor by comparing sensor data fromthe left shoe to the right shoe to determine a difference between theleft and right shoes. A sensory feedback alarm is activated to alert theuser when the difference between the left and right shoes exceeds apredetermined threshold. In accordance with one aspect of the presentinvention, stance phase times or stance phase forces or both of the leftand right shoes are determined and compared based on the sensor data.

In addition, the invention presents a method for analyzing gait andproviding real time feedback on gait asymmetry. Sensor data is receivedfrom a plurality of sensors disposed within left and right shoes whenthe shoes are moved through gait motions by a user of the shoes. Stancephase times or stance phase forces or both of the left and right shoesare determined and compared with an electronic processor based on thesensor data. A difference between stance phase time or stance phaseforces or both between the left and right shoes is determined. A sensoryfeedback alarm is activated to alert the user when the difference of thestance phase times or stance phase forces or both of the left and rightshoes exceed a predetermined threshold.

Furthermore, the invention presents lower extremity feedback system witha plurality of sensors associated with left and right shoes. Amicrocontroller is electronically coupled to the plurality of sensorsand capable of analyzing data from the sensors to determine and comparestance phase times or stance phase forces or both of the left and rightshoes during gaited motion; and to determine a difference between stancephase times or stance phase forces or both of the left and right shoes.A sensory feedback device is electronically coupled to themicrocontroller to sound a sensory alarm when the difference betweenstance phase times or stance phase forces or both of the left and rightshoes exceeds a predetermined threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional features and advantages of the invention will be apparentfrom the detailed description which follows, taken in conjunction withthe accompanying drawings, which together illustrate, by way of example,features of the invention; and, wherein:

FIG. 1 is a schematic view of a lower extremity feedback system inaccordance with an embodiment of the present invention, shown associatedwith shoes worn by a user;

FIG. 2 is a flow chart of a method for analyzing gait and providing realtime feedback on gait asymmetry;

FIG. 3a is an exemplary graph of force measure vs. time for stance phaseof the left foot;

FIG. 3b is an exemplary graph of force measure vs. time for stance phaseof the right foot;

FIG. 3c is an exemplary graph of force measure vs. time as measured by aforce plate for the left foot;

FIG. 3d is an exemplary graph of force measure vs. time as measured by aforce plat for the right foot; and

FIG. 4 is exemplary graphs of force measured vs. time for left and rightfeet through several stance phases and swing phases.

Reference will now be made to the exemplary embodiments illustrated, andspecific language will be used herein to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENT(S)

Reference will now be made to the exemplary embodiments illustrated inthe drawings, and specific language will be used herein to describe thesame. It will nevertheless be understood that no limitation of the scopeof the invention is thereby intended. Alterations and furthermodifications of the inventive features illustrated herein, andadditional applications of the principles of the inventions asillustrated herein, which would occur to one skilled in the relevant artand having possession of this disclosure, are to be considered withinthe scope of the invention.

The embodiments of the present invention described herein provide for alower extremity feedback system and method that evaluate the asymmetryof gait of the user and provide real time feedback if the asymmetry isover a specified threshold. The lower extremity feedback system caninclude a pair of instrumented shoes and a feedback device. In oneaspect, the shoes can be foot-worn monitors that can includemulti-sensor insoles. The terms “shoe” and “shoes” are used broadlyherein to mean any footwear, whether commercially available or custommade for carrying the sensors, such as shoes, sneakers, boots, sandals,slippers, athletic footwear, socks, prosthetic foot or shell of aprosthetic foot, etc. The shoes can include a plurality of sensors thatcan be placed under the insole of the shoes and arranged to measure theforce distribution from the time the heel strikes the floor until thetime the last toe is off the floor. The sensors in the shoe can beoperatively coupled to an electronic processor, such as via a wirelesstransmitter and receiver. The electronic processor can be coupled afeedback alarm. The electronic processor can collect data measured bythe plurality of sensors in each shoe and control feedback by way of thefeedback alarm. The electronic processor can analyze the data todetermine the degree of asymmetry between the shoes during gait. Whenthe degree of symmetry falls below a predetermined threshold, thefeedback alarm will be activated.

As illustrated in FIG. 1, a lower extremity feedback system, indicatedgenerally at 10, in accordance with the present invention is shown foruse in evaluating the asymmetry of gait of a user and providing realtime feedback if the asymmetry is over a predetermined threshold. Thelower extremity feedback system can include a pair of shoes, or left andright shoes 20; a plurality of sensors 40 associated with and carried bythe shoes; an electronic processor 70 operatively coupled to the sensorsvia a wireless transmitter 60 and receiver 80; and a feedback device 90,such as a transducer or speaker. The feedback device could also providetactile feedback, such as vibration, or visual feedback, such as lightsor a display.

The pair of shoes 20 can be an ordinary pair of shoes or boots as knownin the art. For example, the shoes can be sneakers that can be worn on anatural foot or a prosthetic foot of the user. In one aspect of thepresent invention, the sensors can be configured to be disposed incommercially available shoes already obtained by the user, such as witha sensor insert or insole 42. Alternatively, the sensors can be providedin a custom shoe or foot-borne device specifically made for the sensorsand/or user. The insole 42 can be a plastic or rubber insert formedaround the sensors 40. The insert 42 can be sized and shaped to fitwithin the shoe under the user's foot or under the insole. In anotheraspect, the insert 42 can replace the insole of the shoe. The insole 42can position toe sensors 44 in the toe of the shoe 20 and heel sensors46 in the heel of the shoe. Additionally, other sensors can be placed inthe arch or ball location of the sole if desired. Furthermore, othercircuitry, electronics and/or batteries 48 can be places in the insoles.The insoles can be split, as shown, to help place the toe sensors at thetoe, and heel sensors at the heel.

The sensors 40 can include force sensors, bilateral force sensors,strain gages, accelerometers, pedometers, and levels. Additionally,combinations of these types of sensors can be used in order to measure awide variety of dynamic environmental conditions during the gaitedmotion of the user. Other sensors, as known in the art, can also beused.

The sensors 40 are operatively coupled to the electronic processor 70,such as by wireless transmitter 60 and receiver 80. In one aspect, thetransmitter can be a wireless data transmitter that can transmit awireless signal such as a RF signal, an ultra-violet signal, anultra-sonic signal, an infrared signal, and an optical signal. Thetransmitter can transmit data from the sensors to the data receiver 80associated with the processor 70. The data receiver can receive thesensor data transmitted from the data transmitter. The receiver can be awireless data receiver that can be locatable in a remote location fromthe wireless transmitter. For example, the wireless receiver can belocated in a waist pack 72 that can be attached to the shoe wearer'swaist. Additionally, the wireless receiver can be located in a computer.The data receiver can route the sensor data to the electronic processor.In one aspect of the present invention, the data processor can belocated remote from the sensors and/or shoes, such as on a hip or beltworn housing. Alternatively, the data processor can be located in or onthe shoe, or around the ankle or prosthesis. Alternatively, theprocessor and sensors can be formed together on a circuit within theshoe or insole. Alternatively, the processor can be located in awrist-worn device or in a housing that can be put in a pocket.

The electronic processor 70 can process the sensor data received fromthe sensors. The electronic processor 70 can include a computer, amicroprocessor, a microcontroller, and the like. The electronicprocessor can include electronic memory storage as known in the art.Additionally the electronic processor can be powered by a battery powersource 86.

The electronic processor 70 can analyze the sensor data for asymmetry.For example, the electronic processor 70 can compare the sensor datafrom one of the pair of shoes to the other of the pair of shoes in orderto determine the difference or asymmetry between each of the shoes. Inone aspect, the electronic processor 70 can compare the stance phasetime of one of the shoes with the stance phase time of the other of theshoes in order to determine the stance phase time asymmetry of the user.As used in this application, stance phase time is the time the userapplies a force to one of the shoes.

In another aspect, the electronic processor 70 can compare the totalstance phase force applied to one of the shoes with the total stancephase force applied to the other of the shoes in order to determine thestance phase force asymmetry of the user. In yet another aspect, theelectronic processor 70 can determine both the stance phase timeasymmetry and the stance phase force asymmetry. The electronic processorcan compare the sensor data from the shoes, and determine any differencein real time, during gait motion or while the user is walking.

In all these aspects, the electronic processor 70 can compare the stancephase time asymmetry, the stance phase force loading asymmetry, and/or acombination of the asymmetries with preprogrammed and predeterminedthresholds in order to determine if the asymmetries exceed thethreshold. If the asymmetries or combination of asymmetries exceed thepredetermined threshold, the electronic processor 70 can activate thefeedback device 90.

It will be appreciated that the asymmetry thresholds can be determinedfor any specific individual user or the thresholds can be based on datacollected from a statistical population. If the thresholds are based ona specific individual, prior testing and data collection with theindividual wearing the pair of shoed can be conducted in order todetermine a baseline of performance during the gait of the user. Thebaseline can then be used to calculate the thresholds. The predeterminedthreshold can be at least 15% difference between the left and rightshoes.

The feedback device 90 can be electronically coupled to the electronicprocessor 70 and can provide real time feedback to the user. Thefeedback device 90 can be an alarm that can signal to the user when theuser's gait is outside the predetermined threshold. In this way, theuser can adjust his or her gait stance and loading to correct theasymmetrical condition. Advantageously, correcting the gait in real timereduces the undesirable loading on the joints of user thereby reducingthe likelihood of osteoarthritis forming in the joints.

In one aspect, the feedback device 90 can include an audible alarm thatcan be emitted from a speaker. The audible alarm can give auditory cuesto the wearer of the shoes during walking. The auditory alarm canproduce a separate and distinct sound for each of a variety of gaitasymmetry conditions. For example, in the event the stance phase timeasymmetry exceeds the predetermined threshold the auditory alarm cansound a first distinct sound that will alert the user of the shoes tothe phase time asymmetry condition. Similarly, in the event the stancephase force loading asymmetry exceeds the predetermined threshold, theauditory alarm can produce another second distinct sound that isdifferent than the sound used to alert the user to the stance phase timeasymmetry, in order to alert the user to the stance phase force loadingasymmetry. Additionally, another separate and third distinct sound canbe used to alert the user to a combined stance phase time and forceloading asymmetry. Furthermore, the auditory alarm can also produce adifferent sound to alert the user when the user's gait is within anacceptable asymmetry range so as to train the user how it feels to walkor run in an acceptable symmetrical condition.

In another aspect, the feedback device 90 can include otherproprioceptive alarms. For example, the feedback device can include anaudio indicator, a visual indicator, and a vibrator. Otherproprioceptive feedback devices, as known in the art, can also be used.

Referring to FIG. 2, the present invention can also include a method foranalyzing gait and providing real time feedback on gait asymmetry.Initially, the sensors 40 (FIG. 1) can be calibrated 96. Sensor data isreceived 100 and 104 from a plurality of sensors disposed within leftand right shoes 20 (FIG. 1) when the shoes are moved through gaitmotions by user of the shoes. In one aspect of the present invention,the sensor data can include force and/or contact data indicative of theforce applied during gait motion (FIGS. 3a and 3b ) and contact of theshoe with the walking surface, respectively. The sensor data can beanalyzed with an electronic processor by comparing sensor data from oneof the shoes to the other of the shoes to determine a difference 108between the shoes. The processor can also determine the magnitude offorce applied between the shoes. In addition, the processor candetermine the stance phase time of the shoes. Furthermore, the processorcan compare the difference 112 between the stance phase time and/orforce between the shoes and a predetermined threshold. Thus, theseverity of an asymmetrical gait in the user can be determined. Afeedback alarm can be activated 116 to alert the user when the severityof asymmetrical gait exceeds a predetermined threshold.

Receiving sensor data can also include transmitting data from thesensors by a wireless transmitter. The data transmitted by the wirelesstransmitter can be received by a wireless receiver. The data from thewireless receiver can be routed to the electronic processor.

Analyzing the sensor data can also include comparing stance phase timeof one of the shoes with the stance phase time of the other of the shoes(FIGS. 3a and 3b ) in order to determine the stance phase time asymmetryof the user. The total stance phase force applied to one of the shoescan be compared by the electronic processor with the total stance phaseforce applied to the other of the shoes in order to determine the stancephase force loading asymmetry of the user.

Activating the feedback alarm can also include sounding an audible noisefrom a speaker when the stance phase time/force applied to one of thepair of shoes varies with respect to the other of the pair of shoes by apredetermined threshold. A first noise can be sounded when stance phasetime asymmetry exceeds a predetermined threshold. A second noise can besounded when the stance phase force loading asymmetry exceeds apredetermined threshold. A third noise can be sounded when both stancephase time asymmetry and stance phase force loading asymmetry togetherexceed a predetermined threshold. A fourth distinct noise can be soundedfor steps taken by the user that fall within the parameters of thepredetermined threshold.

The method can also include adjusting the predetermined threshold basedon individual calibration data from the user.

It will be appreciated that while the embodiments described hereingenerally focus on amputees, the concepts of the present invention canbe applied to other physiological conditions that can cause anasymmetrical weight distribution on a person's legs. For example,following orthopedic surgery such as a hip replacement, patients oftenneed to initially keep the weight borne on the affected limb underneatha threshold level (e.g. 10% of bodyweight). Overtime, this threshold isincreased, and eventually, patients need to be sure to bear fullbodyweight. The devices described herein could be used to providefeedback if the patient exceeds the threshold or is not bearing fullbodyweight.

Furthermore, osteoarthritis may not be the only problem helped by theconcepts of the present invention. For example, a unilateral amputee isat great risk of becoming a bilateral amputee due to overloading of theintact limb. Thus, the more symmetric a person's walk and minimizing theimpact on a sound limb, the less likely the person will become abilateral amputee. In addition, there is a strong social motivation forperson's with amputations to reduce visible limp.

While the forgoing examples are illustrative of the principles of thepresent invention in one or more particular applications, it will beapparent to those of ordinary skill in the art that numerousmodifications in form, usage and details of implementation can be madewithout the exercise of inventive faculty, and without departing fromthe principles and concepts of the invention. Accordingly, it is notintended that the invention be limited, except as by the claims setforth below.

What is claimed is:
 1. A method for analyzing gait and providing realtime feedback on gait asymmetry to a user, comprising: a) receivingsensor data from a plurality of force sensors within left and rightshoes when the shoes are moved through gait motions by a user of theshoes; b) analyzing the sensor data with an electronic processor locatedremotely from the plurality of sensors, wherein analyzing the sensordata includes determining and comparing stance phase times, theelectronic processor analyzing the sensor data by comparing sensor datato determine a difference between the left and right shoes; and